Method of mounting tubular electrodes inside the vessels of space discharge devices



Dec. 10, 1935. s MCCULLOUGH H/J ATTOI/YEK Patented Dec. 10, 1935 UNITED STATES PATENT OFFICE Frederick S. McCullough, Edgewood, Pa., assignor to The Union National Bank of Pittsburgh,

Pittsburgh, Pa.

Application June 18, 1928, Serial No. 286,370

10 Claims.

My invention relates to joints for uniting tubes, and its broad purpose is to provide a gas-tight or hermetic joint which may be made where operating space is limited.

An object of my invention is to provide a joint which may be completed without external application of heat.

Another object of my invention is to provide a method of constructing an electrical discharge apparatus having a water cooled electrode whose leads project transversely thru the wall of the envelop.

A further object of my invention is to provide a method of constructing an electrical space discharge device having a very low inter-electrode and inter-lead capacity.

My invention possesses other objects and valuable features, some of which will be set forth in the following description of my invention which is illustrated in the drawing forming part of the specification. It is to be understood that I do not limit myself to the showing made by the said description and drawing, as I may adopt varying forms of my invention within the scope of the claims.

Electrical discharge devices are limited as to output by the amount of heat they can dissipate. The limit of heat dissipation by radiation is very quickly reached, and in order to obtain high output within reasonable space water cooling of electrodes, and particularly of anodes, is resorted to. From many points of view the most convenient water cooled electrode is in the form of a coil of tubing with leads, projecting thru the envelop of the device, thru which water may be circulated. The leads must, of course, be either integral with the coil or fused thereto, since no type of temporary connection is known which is sufficiently gas tight to hold the high vacuum required.

The obvious method of constructing such a device is to use a cylindrical glass envelop and to bring the lead tubes thru the ends of the cylinder. For some purposes this is satisfactory, but for power audions, and particularly those to be used at high frequencies, the capacity between the lead tubes and the other electrodes and their leads is a serious disadvantage.

Theoretically a much better method is to bring the lead tubes out thru the side of the envelop. This has not been practical in the past, since getting the coil into the cylinder with leads long enough to project thru the wall required either a very large envelop as compared with the electrodes it housed, or the construction of long and diflicult seals in the envelop. The first method complicated the problems of evacuation and handling. The seals produced by the second method would not only be extremely hard to make but almost impossible properly to degasify.

A third method would be to insert the coil without leads within the envelop, insert the leads thru apertures in the walls into contact with the ends of the coil, and make the joints in situ. The apparent impossibility of sufficiently heating the joint without destroying the envelop has prevented this being attempted in the past. By using the method of my invention, however, this difficulty is removed and the theoretical advantages of the construction set forth may readily be obtained.

Referring to the drawing:

Figure l is an axial sectional view of an audion or thermionic relay made in accordance with my invention and showing one completed joint and one joint with the parts separated.

Figure 2 is an elevation of the heating element used in forming the joint.

My invention comprises essentially a method of uniting tubes which involves heating the junction between the tubes, preferably by radiation, from within their bore. With the objects as above set forth in view it is preferable to use a bonding material such as silver, copper or ,spelter which is fused into the joint, and to carry out the operation in a non-oxidizing atmosphere, such as nitrogen or hydrogen gas.

To illustrate my invention fully and in detail I have chosen to describe the construction of a power audion designed for high frequency operation. A cylindrical glass blank 6 is provided, from which the envelop or bulb of the device is formed, and transverse glass tubes 1 are sealed to the sides of the tube for passing the tubular V anode leads.

Into the blank, thru the open end, is inserted the coiled tube 8 which is to form the anode. The short ends 9 of the coil are bent radially outward, and are preferably slightly reduced in diameter to form a shoulder I I against which rests a ring I2, formed of copper or other material which may be fused to form a satisfactory bond. A lead tube l3, having a slightly belled end I4, is then passed thru the transverse tube 1 and telescoped over the end 9 of the coil so that the ring I2 contacts with the belled end.

Into the bore of the tube is inserted a heating element, conveniently comprising a coil I6 of tungsten or other highly refractory conductor,

provided with leads I! insulated by the refractory ferred, as it serves actively to keep the surfaces of the joint clean, and eliminates the necessity of fluxing the joint, but nitrogen or other inert gas may be used. All of the heat from the element iii passes outward thru the joint, quickly fusing the ring i2 which flows by capillarity into the telescoped joint and completes a hermetic union between the coil 8 and the lead tube l3.

After the second lead tube has been attached to the coil, the tube i is drawn down to a seal 22 with a bridging member 23 which spans a groove 24 in the lead tube, as is described in detail in my co-pending application Patent N 0. 1,897,761, dated February 14, 1933.

A helical grid 26, carried on supporting rods 21 which are spaced by annular collars 28 and secured to a rod or tube 2d by a band 3!, is then inserted in the envelop coaxially with the anode, and the end of the envelop is drawn to a seal 3| similar'to that formed with the anode leads. For lightness the support 29 is preferably a tube, but in this case the inner end 32 is hermetically closed.

From the other end of the envelop a filament 33', carried on lead rods 34 and a dummy 36 which are sealed into a stem 31, is inserted coaxially with the grid, and the stem is fused to the envelop. A shield 38 is preferably fixed to the dummy to catch accidental bombardment from the filament. The filament leads are each provided with a sleeve 39 to which the stem seal is made, as is also described in my above mentioned copending application. A tubulation M is pro-' vided at some suitable part of the envelop for evacuating the device.

It will be seen that the method of my invention permits the manufacture of thermionic tubes and like space discharge devices in which only the active portions of the electrodes are opposed to each other, the leads being brought out at widely separated points and the inter-electrode capacities being correspondingly low. Moreover it permits the parts to be so arranged that the metal to glass seals all operate at relatively low temperature, thus minimizing glass stresses and release of occluded gases from the seals.

I claim: 1'. The method of uniting a tube within an envelope with another tube projecting through through said container, and heating the junction between said tubes with said heating element.

2. The method of constructing a space discharge tube of the type having a coiled electrode Within a glass envelope, which comprises inserting the coiled tubular electrode into the glass envelope through an open end of the envelope,

inserting separate lead-in tubes through glass nipples projecting laterally from said envelope and bringing said lead-in tubes into engagement with the ends of the tubular coiled electrode, ap-

' plying a bonding material to the joints between the lead-in tube and the tubular coiled electrode, and fusing said bonding material to form hermetic joints, then sealing the glass nipples around the lead in tubes, thereafter inserting the other elements into the glass envelope and sealing the in tubes and the ends of the coiled tubular electrode while flowing a non-oxidizing gas through the envelope over the joints during the heating, and, fusing bonding material at said joints to form hermetic joints, thereafter sealing the nipples of the glass envelope around the lead-in tubes, then inserting the other electrodes into the glass envelope and closing the envelope.

4. The method of manufacturing an electric discharge tube in which a high vacuum is to be maintained and in which there is a hollow eleci trode through which fluid is to be circulated, which comprises inserting the hollow electrode in the envelope, thereafter inserting a tubular connector through an openingzin the wall of. the envelope and joining it to one end of the hollow electrode, inserting a second tubular member through another opening in the wall of. the envelope and joining it .to the other end of the hollow electrode, and thereafter sealingv the glass walls of the envelope about said tubular connectors.

5. The method of manufacturing an electrical discharge tube having a fluid-cooled electrode therein, which electrode has extensions thereon to which fluid supply connections can be made, which comprises inserting said electrode in the envelope, inserting a connector tube through a nipple in the glass envelopeand joining its inner end to said electrode, positioning a fusible material at the joint between the inner end of the connector and the portion of said electrode with which the connector isjoined, inserting a heater in the connector and positioning the heater adjacent the joint between the connector and said electrode, thereby heating the fusible material to form a hermetic sealbetween the connector and said electrode, similarly inserting a second OOH. nector tube through a second nipple in the glass envelope and joining said second connector tube to said electrode and similarly forming a hermetic joint between the said second connector and said electrode, and thereafter sealing the nipples of the envelope about the respective connector tubes to form a'hermetic seal around them.

6. The method of manufacturing electric discharge tubes of the'type having a fluid-cooled electrode within an envelope, which comprises inserting said electrode which is to be fluid-cooled in the envelope, subsequently passing fluid supply and outlet connector tubes through the walls of the envelope, forming a fused joint in situ with-. in the envelope between said connector tubes and said electrode, and thereafter sealing the envelope about said connector tubes.

7. The method of assembling an electron tube device having a glass envelope and having an electrode member therein which is provided with a nipple-like portion, which comprises positioning the electrode member within the envelope, thereafter passing a tubular connector member through the wall of the envelope and bringing it into telescopic engagement with the nipple-like portion of the electrode, one of said members having a fusible material applied thereto, introducing an inert gas into the envelope and inserting a heating device into the tubular connector member until it registers with the connection between the nipplelike portion of the electrode member and the tubular connector member, and heating the joint to melt the fusible material.

8. In the manufacture of vacuum tubes, the method of making a connection within the envelope of the tube between a tubular lead-in connector and an electrode wherein the electrode has a nipple-like portion, which comprises mounting the electrode within an envelope, passing a hollow connector through an opening in the wall of the envelope into telescopic engagement with said nipple-like portion, providing a fusible metallic material to the joint between the connector and the nipple-like portion, thereafter heating the joint until the fusible metallic material fluxes, maintaining a non-oxidizing atmosphere about the joint between the telescoping parts to prevent oxidation of the parts or of the molten fusible material, and thereafter sealing the glass envelope around the lead-in connector.

9. In the manufacture of vacuum tubes, the method of making a connection between an element inside the envelope of the tube and a tubular lead-in connection passing through the wall of the envelope, which comprises placing the member in the envelope, passing the connector through an opening in the envelope, bringing the connector and a nipple-like portion of said member into telescopic engagement inside the envelope, heating the telescoping parts and fusing a meltable metal between them, and thereafter sealing the envelope about the lead-in connection.

10. In the manufacture of vacuum tubes, the method of making a connection between an element inside the envelope of the tube and a tubular lead-in connection passing through the wall of the envelope, which comprises placing the member in the envelope, passing the connector through an opening in the envelope, bringing the connector and a nipple-like portion of said member into telescopic engagement inside the envelope, heating the telescoping parts and fusing a meltable metal between them and thereafter sealing the envelope about the lead-in connection, a non-oxidizing atmosphere being maintained within the envelope while the meltable metal is in a state of fusion.

FREDERICK S. McCULLOUGH. 

